Imaging apparatuses employing optical coherence tomography (hereinafter abbreviated to OCT) have hitherto been developed (see PTL 1, an imaging apparatus employing OCT is hereinafter referred to as OCT apparatus). An OCT apparatus illuminates an object while changing the wavelength of the illuminating light, thereby causing reference light and each of reflections that are fed back from different depths of the object to interfere with each other, thereby generating interfering light. Then, frequency components of a temporal waveform representing the intensity of the interfering light are analyzed. Thus, information on a section of the object, specifically, a tomographic image, can be obtained. The OCT apparatus is used in, for example, an examination of an ocular fundus.
Many ocular diseases are difficult to completely cure. Therefore, it is important to find any lesions in the fundus in earlier stages and to start, in earlier stages, any treatment that slows down the spreading of such a lesion over a wide area of the fundus. Particularly, if the lesion reaches the macula, the eyesight is seriously affected. Hence, there is a demand for finding any lesions even if such lesions are still far away from the macula. To meet such a demand, the OCT apparatus used in fundus examinations is expected to have a wider angle of view.
According to PTL 1, to widen the area of the fundus that is observable as a tomographic image, a plurality of tomographic images are connected to one another, whereby a tomographic image of a wide area is obtained. The apparatus disclosed by PTL 1 is an OCT apparatus employing a wavelength-variable light source (a swept-source OCT apparatus). According to PTL 1, examples of the wavelength-variable light source include a fiber-ring resonator and a wavelength-selective filter.